iPhone OS 4.0, which is likely to be the next major update to the OS that powers iPhone, iPod touch, and iPad, will allow third-party apps to run in the background, and users will be able to navigate those open apps via an interface that borrows from Mac OS X’s Exposé. AppleInsider reported on the feature, which was leaked to the site by developers.

It’s long been rumored and reported that iPhone OS 4.0 would include the ability to run apps in the background, but this is the first report of how Apple would allow users to navigate those apps. In current builds, users hit the Home button twice to bring up a view of icon apps that are open. Choosing an icon will cause that app to come to the foreground, leaving the other apps in the background.

Mac OS X’s Exposé feature causes all of the open windows on a system to be displayed in a grid scaled according to the number of such windows - the more apps and windows open, the smaller the representations. AppleInsider pointed out that the iPhone’s smaller display makes such an approach less viable, and with only one window open a time per app, less necessary.

It should be noted that such a feature would also be available to the iPad, unless Apple chose to artficially block it, which isn’t likely.